Peer-to-Peer computing is a popular, relatively new, distributed computing paradigm. It allows for a flexible set of participants to coordinate their resources with little overhead or reliance on central servers/ services and is becoming particularly relevant in mobile computing environments, where peers come and go. Communication between an (unknown) number of peers, which may or may not be online at the same time, is greatly facilitated by the publish/subscribe model. In this chapter, the authors review the stateof- the-art in publish/subscribe systems, focusing on the support for mobile peers in infrastructure-based networks. They propose a novel handoff approach that proactively distributes pub/sub-related information to brokers/superpeers ahead of a peer’s movement. They show through extensive experiments in a small testbed that the new approach has significant performance benefits, compared to the more typical reactive approach, in which pub/sub context is only established after a handoff event occurred.
Opportunistic Composition of Sequentially-Connected Services in Mobile Computing Environments